Biological sciences

Prevalence of the Rhizobium etli-like allele in genes coding for 16S rRNA among the indigenous rhizobial populations found associated with wild beans from the Southern Andes in Argentina

Article Abstract:

Research was conducted to characterize the rhizobial populations naturally associated with wild beans in various areas in the Southern Andes in northwest Argentina. Results suggest that the rhizobial populations nodulating wild beans in virgin field soils of Northwest Argentina are not the only R. etli and R. leguminosarium bv. phaseoli isolates in those soils that are able to associate with Phaseolus vulgaris L. Both the high densities of type I rhizobia induce speculation that P. vulgaris in this center of origin might have coevolved in the symbiosis with Rhizobium spp.

Studies of the physiological and genetic basis of acid tolerance in Rhizobium leguminosarum biovar trifolii

Article Abstract:

Transposon Tn5 is used in an attempt to identify genes that are involved in the tolerance for growth of acid-tolerant Rhibozium leguminosarum biovar trifolii ANU1173 at a low pH on a defined laboratory medium. At least two loci (mutants AS28 and AS25) of either plasmid or chromosomal location are necessary for the growth of this strain of media at a pH of less than 4.8. The cytoplasmic pH are controlled by acid sensitive mutants in a restricted way.

Involvement of genes on a megaplasmid in the acid-tolerant phenotype of Rhizobium legominosarum biovar trifolii

Article Abstract:

The importance of the second largest megaplasmid of Rhizobium leguminosarum for different cellular functions is discussed. Plasmid curing and mobilization techniques were used in the experiments that maintained acid tolerance, symbiotic nitrogen fixation, lipopolysaccharide and exopolysaccharide syntheses and cell mobility as its parameters. The necessity of the megaplasmid was demonstrated.